1. Technical Field
This invention relates to methods and apparatus for cutting elastomeric materials at low skive angles, in particular cutting layered composites of elastomeric materials including layers containing reinforcing materials.
2. Background of the Invention
Various methods and apparatus have been used for the cutting of sheets of elastomeric material. Such elastomeric material might consist of single sheets of homogeneous material, or multiple layered sheets of materials having properties that are different from one another. In the case of multiple layered sheets of elastomeric material that, for various reasons, need to be cut, one or more of the layers might contain reinforcing cords or fibers made of metal or fabric. Such reinforcing cords or fibers might be part of a woven reinforcing fabric, or they might be simply aligned in such a way as to be parallel to one another. Furthermore, the elastomeric materials that are to be cut may or may not be cured or vulcanized at the time of cutting.
Prior art cutting methods and apparatus include cutting wheels, ultrasonic cutters, scissor type cutters, guillotine knives, wire cutters and vibrating scroll cutters whose active cutting principle is a saw blade or a tensioned wire.
While such prior art cutting methods are effective to varying degrees, each as disadvantages. For example, the guillotine knife is somewhat effective in cutting composite elastomeric materials, but it has the disadvantage of having a tendency to deform the cut surfaces of the elastomeric material as the knife penetrates the material. Such deformation of the cut edge increases the difficulty of subsequent splicing the ends of the elastomeric material. Moreover, the guillotine knife produces a continually degraded cut surface as the blade becomes dull and/or as small pieces of elastomer began to build up on the blade. Yet another disadvantage was the inability of the blade to cut at an angle less than 30 degrees relative to the plane of the material being cut. The guillotine blade also tends to generate heat during the cutting process such that, as numerous cuts are made, the temperature of the knife becomes sufficiently elevated in some cases to induce precuring of unvulcanized elastomer in the region of the cut, which then inhibits subsequent proper splicing the cut edges.
Another prior art cutting system and method, disclosed in U.S. Pat. No. 5,638,732, employs a cutting wire. This system could not, however, be used to cut preassembled elastomeric composite sheets containing reinforcing cords because the reinforcing cords themselves, though aligned more or less parallel to the direction of the cut, get severed. This deficiency is actually inherent to nearly every prior art cutting technology (including ultrasonic knives) that cut composite elastomeric preassemblies at relatively low skive angles. That is to say, nearly all prior art cutting methods tended to cut the parallel-aligned cords that are used to reinforce one or more layers of reinforced ply. (The cut is, ideally, intended to be made between the parallel-aligned reinforcing cords.) The only prior art exception being the scroll cutter, which could cut at low skive angles without also risking cutting the reinforcing cords.
The scroll cutter cannot, however, initiate its cut within the central region of a sheet of preassembled composite elastomeric sheets, because of its geometry, which includes a wire held at each end by a fixture. The scroll cutter must start its cut from the side of the preassembly, such that the cutting has difficulty entering the ply without splitting the reinforcing cords. Even at a 90 degree skive angle, the reliability of not splitting cords is in question. At low skive angles it becomes exponentially difficult to enter the ply without splitting a ply cord. Sometimes the reinforced ply end will be buried under the other layers, such as, in the case of tire manufacturing, the sidewall layer or other layers such as the extreme edge of the preassembly within the context of envelope construction. This adds another dimension of difficulty for the wire scroll cutter to cut reliably preassembly with reinforced layers, such as specifically the ply of tires.
Ultrasonic cutting systems as disclosed in U.S. Pat. No. 5,265,508, can cut stock material at low skive angles. However, they require that the material be secured to an anvil during cutting.
Another system, disclosed in U.S. Pat. No. 4,922,774, employs an ultrasonic cutting device which vibrates a knife that moves across an elastomeric strip. However, this system is limited to cutting angles of between 10 and 90 degrees, and it does not provide for cutting between parallel disposed, reinforcement cords within the strip, which is to say, the cords can get cut.
A significant problem with the prior art cutting systems and methods is the inability to cut at angles less than 30 degrees relative to the plane of the elastomeric layers being cut without deformation or precuring the material. This can be a problem in, for example, automated tire building operations wherein the cutting has to be done precisely and quickly and where the cutter can also provide improvements to the cut surface which is subsequently to be spliced.
An ideal cutting method and apparatus should be able to make cuts at low angles (relative to the plane of the elastomeric sheet being cut), and it should be able to do so without cutting the parallel-aligned reinforcing cords between which the cutter is ideally to move. It should also be able to make these low angle cuts rapidly and reliably.
It is an object of the present invention to provide method and apparatus for cutting single or multilayered flat sheets of elastomeric materials, one or more layers of which are reinforced with cords which are aligned parallel to one another and oriented in the direction of the cut, the method and apparatus being as defined in one or more of the appended claims and, as such, having the capability of being constructed to accomplish one or more of the following subsidiary objects.
One object of the present invention to provide a method and apparatus for cutting segments of cord-reinforced elastomeric material from long, multilayered flat sheets of cord-reinforced elastomeric material, such method and apparatus overcoming the disadvantages and limitations of the prior art methods and devices.
Another object of the present invention to provide a method and apparatus for cutting segments of material from long multilayered flat sheets of cord-reinforced elastomeric material without cutting the reinforcing cords that are more or less aligned with the direction of the cut.
It is another object of the present invention to provide a method and apparatus for cutting segments of material from long multilayered flat sheets of cord-reinforced elastomeric materials by initiating the cut at a location that is between the lateral edges of the sheet of elastomeric material.
Yet another object of the present invention to provide a method and apparatus for initiating the cutting segments of material from multilayered flat sheets of cord-reinforced elastomeric materials without cutting the reinforcing cords.
Another object of the present invention to provide a method and apparatus for cutting segments of material from long multilayered flat sheets of cord-reinforced elastomeric materials by the controllable penetration of the cutting knifes such as to perform the cutting in a such a way that intentionally dulled edges of the cutting knives are in close proximity to the reinforcing cords, thereby protecting the reinforcing cords from being cut.
Another object of the present invention is to provide a method and apparatus for cutting segments of material from long multilayered flat sheets of cord-reinforced elastomeric materials at skive or cutting angles that can be varied between angles of about 5 degrees and about 40 degrees with respect to the plane of the sheet.
Still another object of the present invention to provide method and apparatus for cutting segments of material from long multilayered flat sheets of cord-reinforced elastomeric materials at skive angles or cutting angles that can be controllably varied between about 5 degrees and about 40 degrees with respect to the plane of the sheet at the beginning of the cutting operation; and
Finally another object of the present invention to provide method and apparatus for cutting segments from long multilayered flat sheets of cord-reinforced elastomeric materials at skive or cutting angles which can be varied between angles of about 5 degrees and about 40 degrees with respect to the plane of the sheet during the cutting operation.
The invention herein described is a method for cutting segments of elastomeric material from a long sheet of multilayered elastomeric material, at least one layer of which contains parallel aligned reinforcing cords. The cutting method employs the use of a penetrator/separator and two ultrasonic knives of a double-edged, stiletto type. The penetrator/separator makes an initial opening in the sheet of elastomeric material, penetrating it while separating, without severing, the reinforcing cords. The tip of the penetrator/separator can be heated to facilitate penetration, and the tip is blunt or dulled to minimize the potential for severing the parallel-aligned, reinforcing cords. The sides of the penetrator/separator are tapered so that the opening created in the elastomeric sheet can be controllably widened according to the depth to which the penetrator/separator is inserted into and through the opening it creates. The initial penetration is made at some location inwards of the two sides of the sheet being cut. The penetrator/separator is initially substantially perpendicular to the sheet being penetrated. After the opening is made in the elastomeric sheet, the two ultrasonic knives are inserted into the opening, one on either side of the penetrator/separator. The two knives might be inserted into the opening before they and the penetrator/separator are angularly reoriented to an angle of less than 90 degrees, i.e. between 5 degrees and 40 degrees, with respect to the plane of the elastomeric sheet being cut, or the two knives might be inserted into the opening after the penetrator/separator has been angularly reoriented to an angle of less than 90 degrees with respect to the plane of the elastomeric sheet being cut. The ultrasonic knives, after insertion and angular adjustment, make the cut by moving apart from one another and from the penetrator/separator. The skive angle or cutting angle of the knives can be adjusted during the cutting process, each knife independently of the other or in concert with the other. The skive angle of each knife is adjustable between about 5 degrees and about 40 degrees within the plane perpendicular to the direction of the cut. The depth to which each ultrasonic knife is inserted into the elastomeric sheet is controllable. The tip of each ultrasonic knife blade is dulled to minimize the potential for cutting of the parallel-aligned reinforcing cords most adjacent to the line along with the cut is being made.
Other benefits and advantages of the invention will become apparent to those skilled in the art to which it pertains upon a reading and understanding of the following detailed specification.